1. Field of the Invention
This invention relates in general to method and apparatus for producing coffee, tea or other beverages during a single cycle. Particularly, this invention is an improvement in coffee brewing machines and it allows the lower chamber to drain more rapidly and allows the mechanism to brew more cups between cleaning the filter element.
2. Description of the Related Art
The present invention is an improvement in single cup beverage brewers such as described in U.S. Pat. No. 5,351,604 which issued on Oct. 4, 1994 and U.S. Pat. No. 5,349,897 which issued on Sep. 27, 1994 both of which were improvements on the apparatus described in U.S. Pat. No. 3,565,641 which issued Feb. 23, 1971, all of which are assigned to the assignee of the present application. These three patents describe methods and apparatus for producing a single cup of coffee. The apparatus consists of an upper chamber which is open at the top to allow coffee and hot water to enter and be mixed. For most of the cycle the upper chamber is tightly sealed to a lower chamber.
The top of the lower chamber has a filter element that allows liquids to move between the two chambers. The lower chamber contains a piston which can move air up and down. The piston first moves upwardly to force air through the mixture of coffee and water in the upper chamber. This movement of air agitates the coffee and water. The piston then travels downwardly and draws the liquid coffee through the filter element. The liquid coffee is drawn down until it reaches an opening in the lower chamber where it pours out along a spout. The chambers are then separated to so that the spent coffee grounds can be removed.
The apparatus described in U.S. Pat. No. 5,351,604 has a fixed permanent filter element on the top of the lower chamber. The coffee grounds are removed by a wiper which traverses the filter element and scrapes the residue until it falls into a waste container. As each cup of coffee is brewed more and more residue accumulates on the filter element. Airflow through the filter element becomes restricted because of this residue. When the liquid coffee tries to exit the lower chamber, it is restricted as there continues to be a vacuum in the lower chamber. Air eventually seeps into the lower chamber and allows the lower chamber to empty but this can take several seconds. This delay time can be reduced by cleaning the filter element to remove the residue.